AS 3740-2021 Waterproofing Standard: Complete Guide
Everything Sydney homeowners and builders need to know about the Australian waterproofing standard that governs all wet area construction in NSW.
Last updated: 15 January 2026
What Is AS 3740-2021?
AS 3740-2021 is the Australian Standard for waterproofing of domestic wet areas. It sets out the minimum requirements for waterproofing materials, design, and installation in residential buildings across Australia. In NSW, compliance with this standard is referenced by the Building Code of Australia (NCC) and is mandatory for all wet area construction and renovation in Sydney. The 2021 revision updated several key requirements from the previous 2010 edition, including clarified membrane termination details and improved testing requirements.
Scope: What Areas Does It Cover?
AS 3740-2021 applies to all domestic wet areas including bathrooms, shower recesses, laundries, toilets, and any other area where water is used or may accumulate. In Sydney homes, this typically covers bathrooms, ensuites, laundries, and indoor spa areas. The standard also covers balconies that adjoin wet areas and any area where a floor waste is installed. It does not cover external waterproofing such as roofs, basements, or standalone balconies, which are governed by other standards and codes.
Wet Area Classifications
The standard classifies wet areas based on water exposure levels. Shower areas (including the shower recess floor and walls to a height of 1800mm above the finished floor) are classified as high-exposure areas requiring full membrane waterproofing. Bathroom floors outside the shower area, laundry floors, and toilet floors are classified as lower-exposure areas but still require waterproofing. The classification determines the membrane type, thickness, and application method required for compliance.
Membrane Requirements
Waterproofing membranes used in Sydney wet areas must comply with AS 4858 (wet area membrane performance) or AS 3740 Class III minimum bond strength requirements. Membranes must be applied in at least two coats to achieve a minimum dry film thickness (DFT) as specified by the manufacturer. All internal corners, floor-wall junctions, and penetrations must be reinforced with bond-breaker tape or fabric. The membrane must extend up walls to specified heights and be terminated correctly to prevent water tracking behind the membrane.
Required Wall Heights
Wall waterproofing heights are critical for compliance. In shower recesses, the membrane must extend at least 1800mm above the finished floor level on all shower walls. For bathroom walls outside the shower area, the membrane must extend at least 150mm above the finished floor level. Around baths, the membrane must extend at least 150mm above the bath rim on walls adjacent to the bath. These are minimum heights — many Sydney waterproofers apply membrane higher for added protection.
Testing and Verification
After membrane application and before tiling, a flood test is required to verify the waterproofing is effective. The shower recess or wet area floor is flooded with water to a depth of approximately 25mm and left for a minimum period (typically 24 hours) to check for leaks. The waterproofer should document the test results and photograph the completed membrane before it is covered by tiles or other finishes. This documentation forms part of the waterproofing certificate.
Compliance in Sydney and NSW
In NSW, all waterproofing work on residential buildings must comply with AS 3740-2021 as referenced by the NCC. Waterproofing must be carried out by a licensed contractor holding a valid NSW Fair Trading licence. Upon completion, the waterproofer should issue a certificate of compliance confirming the work meets the standard. For renovation work in Sydney, the principal certifying authority (PCA) may require evidence of waterproofing compliance before issuing an occupation certificate. Strata buildings in Sydney have additional requirements around documentation and owner corporation approval.
AS 3740-2021 Waterproofing Standard FAQs
Yes. AS 3740-2021 is referenced by the National Construction Code (NCC), which is adopted by NSW legislation. All domestic wet area waterproofing in Sydney must comply with this standard.
The 2021 revision clarified membrane termination requirements, updated testing procedures, improved guidance on junction details, and aligned with updated membrane performance standards.
Only contractors holding a valid waterproofing licence issued by NSW Fair Trading can perform waterproofing work in Sydney. Always verify their licence number before engaging them.
Yes. Even if you are doing a bathroom renovation yourself in Sydney, the waterproofing must comply with AS 3740-2021 and should be inspected by a licensed professional or building certifier.
Your licensed waterproofer should issue a certificate of compliance upon completing the work. This certificate confirms the waterproofing meets AS 3740-2021 and is needed for building sign-off.
Related Resources
Related Services
Related Problems
Need Expert Waterproofing Advice?
Get free, no-obligation quotes from licensed waterproofing contractors in Sydney who understand AS 3740-2021 compliance and NSW requirements.
- NSW Fair Trading licensed contractors
- AS 3740-2021 compliant waterproofing
- Free quotes with no obligation
Get 3 Free Quotes
Compare licensed waterproofing contractors in Sydney